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Linux 2.6 - man page for write (linux section 1posix)

WRITE(P)			    POSIX Programmer's Manual				 WRITE(P)

NAME
       write - write to another user

SYNOPSIS
       write user_name [terminal]

DESCRIPTION
       The  write  utility  shall read lines from the user's standard input and write them to the
       terminal of another user. When first invoked, it shall write the message:

	      Message from sender-login-id (sending-terminal) [date]...

       to user_name. When it has successfully completed the  connection,  the  sender's  terminal
       shall  be alerted twice to indicate that what the sender is typing is being written to the
       recipient's terminal.

       If the recipient wants to reply, this can be accomplished by typing:

	      write sender-login-id [sending-terminal]

       upon receipt of the initial message. Whenever a line of input as delimited by an NL,  EOF,
       or EOL special character (see the Base Definitions volume of IEEE Std 1003.1-2001, Chapter
       11, General Terminal Interface) is accumulated while in canonical input mode, the  accumu-
       lated  data  shall be written on the other user's terminal.  Characters shall be processed
       as follows:

	* Typing <alert> shall write the alert character to the recipient's terminal.

	* Typing the erase and kill characters shall affect the sender's terminal in  the  manner
	  described   by   the	 termios   interface   in   the   Base	 Definitions   volume  of
	  IEEE Std 1003.1-2001, Chapter 11, General Terminal Interface.

	* Typing the interrupt or end-of-file characters shall cause write to write an	appropri-
	  ate message ( "EOT\n" in the POSIX locale) to the recipient's terminal and exit.

	* Typing  characters from LC_CTYPE classifications print or space shall cause those char-
	  acters to be sent to the recipient's terminal.

	* When and only when the stty iexten local mode is enabled, the existence and  processing
	  of  additional  special  control  characters and multi-byte or single-byte functions is
	  implementation-defined.

	* Typing other non-printable characters shall cause implementation-defined  sequences  of
	  printable characters to be written to the recipient's terminal.

       To  write  to a user who is logged in more than once, the terminal argument can be used to
       indicate which terminal to write to; otherwise, the recipient's terminal is selected in an
       implementation-defined  manner  and  an	informational  message is written to the sender's
       standard output, indicating which terminal was chosen.

       Permission to be a recipient of a write message can be denied or granted  by  use  of  the
       mesg  utility. However, a user's privilege may further constrain the domain of accessibil-
       ity of other users' terminals. The write utility shall fail when the user lacks the appro-
       priate privileges to perform the requested action.

OPTIONS
       None.

OPERANDS
       The following operands shall be supported:

       user_name
	      Login  name  of  the  person  to whom the message shall be written. The application
	      shall ensure that this operand is of the form returned by the who utility.

       terminal
	      Terminal identification in the same format provided by the who utility.

STDIN
       Lines to be copied to the recipient's terminal are read from standard input.

INPUT FILES
       None.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of write:

       LANG   Provide a default value for the internationalization variables that  are	unset  or
	      null. (See the Base Definitions volume of IEEE Std 1003.1-2001, Section 8.2, Inter-
	      nationalization Variables for the precedence of internationalization variables used
	      to determine the values of locale categories.)

       LC_ALL If  set  to a non-empty string value, override the values of all the other interna-
	      tionalization variables.

       LC_CTYPE
	      Determine the locale for the interpretation of sequences of bytes of text  data  as
	      characters  (for	example, single-byte as opposed to multi-byte characters in argu-
	      ments and input files). If the recipient's locale does not use an LC_CTYPE  equiva-
	      lent to the sender's, the results are undefined.

       LC_MESSAGES
	      Determine the locale that should be used to affect the format and contents of diag-
	      nostic messages written to standard error and informative messages written to stan-
	      dard output.

       NLSPATH
	      Determine the location of message catalogs for the processing of LC_MESSAGES .

ASYNCHRONOUS EVENTS
       If an interrupt signal is received, write shall write an appropriate message on the recip-
       ient's terminal and exit with a status of zero. It shall take the standard action for  all
       other signals.

STDOUT
       An  informational  message shall be written to standard output if a recipient is logged in
       more than once.

STDERR
       The standard error shall be used only for diagnostic messages.

OUTPUT FILES
       The recipient's terminal is used for output.

EXTENDED DESCRIPTION
       None.

EXIT STATUS
       The following exit values shall be returned:

	0     Successful completion.

       >0     The addressed user is not logged on or the addressed user denies permission.

CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.

APPLICATION USAGE
       The talk utility is considered by some users to be a more usable  utility  on  full-screen
       terminals.

EXAMPLES
       None.

RATIONALE
       The  write  utility  was  included  in this volume of IEEE Std 1003.1-2001 since it can be
       implemented on all terminal types. The standard developers considered  the  talk  utility,
       which  cannot  be implemented on certain terminals, to be a "better" communications inter-
       face. Both of these programs are in widespread use on historical  implementations.  There-
       fore, the standard developers decided that both utilities should be specified.

       The format of the terminal name is unspecified, but the descriptions of ps, talk, who, and
       write require that they all use or accept the same format.

FUTURE DIRECTIONS
       None.

SEE ALSO
       mesg , talk , who , the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 11,  Gen-
       eral Terminal Interface

COPYRIGHT
       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2003 Edition, Standard for Information Technology  --  Portable	Operating  System
       Interface  (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by
       the Institute of Electrical and Electronics Engineers, Inc and  The  Open  Group.  In  the
       event  of  any  discrepancy  between this version and the original IEEE and The Open Group
       Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					 WRITE(P)


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